Signal Processing Device and Signal Processing Method

1. A signal processing device comprising a receiver configured to receive a modulation signal that has been subjected to frequency shift keying, by dividing a reference transmission frequency by using a first or second transmission division ratio selected in accordance with a value of first communication data, wherein the receiver includes: a first demodulator configured to obtain the first communication data by demodulating the modulation signal on the basis of a demodulation control signal; and a demodulation control signal generator configured to generate the demodulation control signal on the basis of the modulation signal and the demodulated first communication data, and wherein the demodulation control signal generator includes: a first frequency divider configured to divide a frequency of a first comparison signal that is one of the modulation signal and the demodulation control signal, by a first or second reception division ratio selected in accordance with a value of the demodulated first communication data; a frequency control signal generator configured to generate a frequency control signal for controlling a frequency of the demodulation control signal on the basis of a frequency of a second comparison signal that is the other of the modulation signal and the demodulation control signal, and a frequency of the first comparison signal obtained by division by the first or second reception division ratio; and a first oscillator configured to oscillate at a frequency based on the frequency control signal to generate the demodulation control signal.

2. The signal processing device according to claim 1 , wherein the frequency of the demodulation control signal follows fluctuations in the reference transmission frequency by adjusting the first transmission division ratio, the second transmission division ratio, the first reception division ratio, and the second reception division ratio to satisfy a predetermined relational expression.

3. The signal processing device according to claim 1 , wherein the first frequency divider divides a frequency of the second comparison signal by a third reception division ratio, and wherein the frequency control signal is generated on the basis of a frequency of the second comparison signal obtained by division by the third reception division ratio and a frequency of the first comparison signal obtained by division by the first or second reception division ratio.

4. The signal processing device according to claim 1 , wherein a relational expression of N 2 /N 1 =M 2 /M 1 is satisfied, where f 1 is the reference transmission frequency, f 2 is a frequency of the demodulation control signal, N 1 (N 1 is an integer) is the first transmission division ratio, M 1 (M 1 is an integer satisfying N 1 <M 1 ) is the second transmission division ratio, N 2 (N 2 is an integer) is the first reception division ratio, and M 2 (M 2 is an integer satisfying N 2 <M 2 ) is the second reception division ratio, and wherein the frequency of the demodulation control signal is controlled such that a relational expression of f 2 =(N 2 /N 1 )×f 1 /K (K is an integer) is satisfied.

5. The signal processing device according to claim 1 , wherein a relational expression of N 1 ×N 2 =M 1 ×M 2 is satisfied in a case where f 1 is the reference transmission frequency, f 2 is a frequency of the demodulation control signal, N 1 (N 1 is an integer) is the first transmission division ratio, M 1 (M 1 is an integer satisfying N 1 <M 1 ) is the second transmission division ratio, N 2 (N 2 is an integer) is the first reception division ratio, and M 2 (M 2 is an integer satisfying N 2 <M 2 ) is the second reception division ratio, and wherein the frequency of the demodulation control signal is controlled such that a relational expression of f 2 ={f 1 /(N 1 ×N 2 )}×K (K is an integer) is satisfied in the case.

6. The signal processing device according to claim 1 , wherein the modulation signal fluctuates in accordance with a value of second communication data, and wherein the receiver further includes a second demodulator configured to obtain the second communication data by demodulating the frequency control signal on the basis of fluctuations in the modulation signal detected from the frequency control signal.

7. The signal processing device according to claim 1 , wherein the receiver determines at least one of the frequency of the demodulation control signal, the first reception division ratio, and the second reception division ratio in a calibration mode period, and wherein demodulation of the modulation signal is started after the end of the calibration mode period.

8. The signal processing device according to claim 1 , wherein the first demodulator includes: a delay adder configured to generate a delay signal by adding a delay time to the modulation signal, and a comparator configured to obtain the first communication data by comparing the modulation signal with a delay signal of the modulation signal.

9. The signal processing device according to claim 1 , wherein the first demodulator includes: a first delay adder configured to generate a first delay signal by adding a first delay time to the modulation signal, a first comparator configured to generate a third comparison signal by comparing the modulation signal with the first delay signal, a second delay adder configured to generate a second delay signal by adding a second delay time to the modulation signal, a second comparator configured to generate a fourth comparison signal by comparing the opposite-phase signal of the modulation signal with the second delay signal, and a third comparator configured to obtain the first communication data by comparing the third comparison signal with the fourth comparison signal.

10. The signal processing device according to claim 1 , further comprising: a transmitter configured to transmit the modulation signal; and an insulator configured to provide insulation between the transmitter and the receiver, wherein the transmitter includes: a second oscillator configured to oscillate at the reference transmission frequency to generate a reference transmission signal; and a third frequency divider configured to divide the reference transmission frequency by the first or second transmission division ratio selected in accordance with a value of the first communication data to generate the modulation signal, wherein the insulator generates a high-frequency electromagnetic field on the basis of the modulation signal, and wherein the insulator generates a high-frequency electrical signal on the basis of the high-frequency electromagnetic field, and wherein the receiver receives the modulation signal by receiving the electrical signal.

11. The signal processing device according to claim 10 , wherein the insulator includes at least a transformer.

12. The signal processing device according to claim 10 , wherein the insulator includes at least a capacitor element.

13. The signal processing device according to claim 10 , further comprising: a rectifier configured to convert an electrical signal from the insulator into a direct current voltage; and a power supply circuit configured to convert the direct current voltage from the rectifier into a predetermined output voltage.

14. The signal processing device according to claim 10 , wherein the receiver includes a variable load device configured to change a load in accordance with a value of third communication data, and wherein the transmitter includes a third demodulator configured to obtain the third communication data by demodulating an envelope output of the voltage or current calculated by an envelope detector on the basis of fluctuations in the current or voltage of the modulation signal transmitted to the insulator, the fluctuations occurring with fluctuations in the load on the variable load device.

15. A signal processing method performed by a signal processing device configured to receive a modulation signal that has been subjected to frequency shift keying, by dividing a reference transmission frequency by using a first or second transmission division ratio selected in accordance with a value of first communication data, the signal processing method comprises: (a) obtaining the first communication data by demodulating the modulation signal on the basis of a demodulation control signal; and (b) generating the demodulation control signal on the basis of the modulation signal and the demodulated first communication data, wherein (b) includes: dividing a frequency of a first comparison signal that is one of the modulation signal and the demodulation control signal, by a first or second reception division ratio selected in accordance with a value of the demodulated first communication data, generating a frequency control signal for controlling a frequency of the demodulation control signal on the basis of a frequency of a second comparison signal that is the other of the modulation signal and the demodulation control signal, and a frequency of the first comparison signal obtained by division by the first or second reception division ratio, and oscillating at a frequency based on the frequency control signal to generate the demodulation control signal.